Procolophon reached a length up to 30 cm.[1] The skull was solid but some species did evolve a temporal fenestra in the skull independently of other reptiles. There was one backward facing cheek spike, but its function is debated; it may have been for muscle attachment. Eyes were large and may have had acute day or night vision. The teeth were peg-like and suitable for crushing of plant matter. The front of the skull was short and blunt with the nasal opening very close to the mouth.

The vertebrae were robust with a rounded rib cage composed of many small weak ribs. Legs were short, thickly built with short phalanges; this suggests an animal that burrowed and did not run fast.